1. Field of Invention
The present invention generally relates to a lighted display, e.g., for signage or other visual communication, comprising multimodal illumination components arranged for illuminative operation even during temporal loss of power to the display.
2. Brief Description of the Related Art
Many forms of visual displays must be readily visible under a wide variety of lighting conditions. As discussed herein, the term xe2x80x9cdisplayxe2x80x9d is to be understood as broadly including informational, pictorial or graphic displays, e.g., containing alphabetic and/or numeric text, graphic components, icons, symbols or other visually discernable indicia. Specific examples include: signage such as scoreboards, schedule displays in airport terminals, bus stations, train stations, and stadiums; instrument displays, such as those found in the instrument panels of aircraft cockpits, automobiles, and in other vehicles; and display panels on industrial and office equipment, appliances, telephones, numeric/alphanumeric keypads, computer/typewriter keyboards, and other human-machine interface structures and components. To provide sufficient illumination under low ambient lighting conditions such displays typically contain integral lighting components, such as incandescent bulbs, LEDs, fluorescent tubes, or electroluminescent panels, coupled in powered relationship to a power supply or other energy source or conversion means. In visibility-critical applications, such powered-lighting displays often also include a backup power system, e.g., an uninterruptable power supply (UPS), redundant power source, battery back-up, or other power delivery means, to provide illumination in the event of failure or interruption of power delivery to the lighting structure or component(s) of the display.
As one example of lighted displays known in the art, Klein U.S. Pat. No. 4,217,625 discloses a front-lighted display for an instrument dial face and pointer comprising in one embodiment a plurality of LEDs arranged around the front of the dial face for direct illumination, and in another embodiment, a mechanical digital counter readout is frontally illuminated with LEDs, with the LEDs being shielded from direct view by a reflector. Klein U.S. Pat. No. 4,044,708 discloses a transilluminated instrument, with LEDs arranged around the back side of the dial face, illuminating a reflective diffuser surface and thereby backlighting the instrument. In an alternative embodiment, a separate LED directly backlights a dial pointer.
Muggli U.S. Pat. No. 5,456,955 discloses a back-illuminated display using a clear separation layer between an underlying light-transmissive/diffusion layer and an overlying light-absorptive layer to facilitate etching of indicia through the light-absorptive layer by a neodymium YAG laser, for applications such as providing keypad alphanumeric indicators.
Lerner U.S. Pat. No. 5,433,024 discloses an advertising sign comprising a tapered transparent acrylic plate illuminated at its thickest edge, and backlighting indicia applied to the oblique faces of the plate.
Streit U.S. Pat. No. 4,684,939 describes an illuminated LCD display, comprising a fluorescent light source and shielding reflector positioned to illuminate the display from the direction that achieves optimum contrast of the LCD active area for the observer under ambient diff-use illumination conditions.
The use of fluorescent materials to enhance the visibility of signs is known in the art. Fluorescent dyes and pigments are commonly used to alter color and enhance contrast in such applications, but are ineffective without incident light.
Fluorescent phosphors are also employed to down-convert photonic energy for illumination. Lengyel et al. U.S. Pat. No. 5,907,222 describes a backlit sign in which a cavity behind the display is coated with a fluorescent phosphor. A cavity-mounted UV excites the phosphor, causing it to emit light in the visible spectrum to backlight the display.
All actively illuminated displays of the prior art suffer the significant deficiency that they become unreadable in low or no ambient light conditions, e.g., upon a failure or interruption of power delivery to the display.
In critical applications, such as instrumentation in aircraft and other vehicles, or signs demarcating emergency exits, a backup power source for illumination must be provided, increasing the cost, complexity, and labor requirements (inspection, testing and maintenance) of the overall system.
In addition to failure from loss or interruption of power, all actively illuminated displays suffer the deficiency of loss of readability through failure of one or more of the active illumination elements (such as incandescent bulbs, LEDs, fluorescent tubes, etc.) or their associated circuitry components. These displays may be designed to include various redundancies to increase their reliability, but this also increases cost, complexity, and maintenance requirements of the overall system.
It is thus an object of the present invention to provide a display with a high visibility/readability under daylight or normal ambient illumination, as well as under low or no ambient light conditions, as well as following failure of the active light source or its associated power delivery components.
Other objects and advantages of the invention will be more fully appreciated with reference to the ensuing disclosure and appended claims.
The present invention relates to an illuminated display that is susceptible to interruption or termination of active lighting capability and provides passive lighting capability in such circumstances.
In one embodied aspect, the illuminated display comprises:
an active illumination source providing said active lighting capability; and
a display member (i) arranged in light-receiving relationship to the active illumination source and (ii) containing photoluminescent pigment incorporated therein in sufficient amount and distribution to illuminate the display during said interruption or termination of active lighting capability, to provide said passive lighting capability.
The illuminated display may further comprise fluorescent dyes/pigments arranged in photoluminescent light-receiving relationship to the display member containing the photoluminescent pigment, whereby the fluorescent dyes/pigments down-converts photoluminescent light from the display member during the interruption or termination of active lighting capability.
The invention relates in another aspect to an illuminated display that is susceptible to interruption or termination of active lighting capability and provides passive lighting capability in such circumstances, wherein the illuminated display comprises:
an active illumination source providing said active lighting capability;
an optically non-opaque display member (i) forming at least part of a housing for the illuminated display, (ii) arranged in light-receiving relationship to the active illumination source and (iii) containing photoluminescent pigment incorporated therein in sufficient amount and distribution to illuminate the display during the interruption or termination of active lighting capability, to provide the aforementioned passive lighting capability; and
a fluorescent dye/pigment on or in the display member, for down-converting photoluminescent light from the display member during the interruption or termination of active lighting capability.
In a method aspect, the invention relates to a method of providing passive lighting capability for an actively illuminated display including an active illumination source that is susceptible to interruption or termination of active lighting capability, so that light is provided to the display during said interruption or termination. The method comprises:
arranging in light-receiving relationship to the active illumination source a display member containing photoluminescent pigment incorporated therein in sufficient amount and distribution to illuminate the display during the interruption or termination of active lighting capability, to provide the aforementioned passive lighting capability.
A further aspect of the invention relates to a method of providing sustained illumination, comprising coupling a powered illumination source with a photoluminescent pigment arranged in light-receiving relationship to the powered illumination source, whereby the photoluminescent pigment provides illumination in the event of failure of the powered illumination source.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.